Establishment of comprehensive evaluation system for cold tolerance and screening of cold-tolerance germplasm in peanut

Low temperature in early spring is the key factor limiting the yield and quality of peanut in Northeast China, which mainly occurs at germination and seedling stages. The selection and breeding of cold-tolerant cultivars are the most direct and effective means to solve the problem of chilling injury in agricultural production. In this study, 68 peanut cultivars mainly planted in Northeast China were used as experimental materials, and their cold tolerance was evaluated at germination and seedling stages in the climatic chamber and field, respectively. At germination stage, we found that the cold treatment at 6℃ for seven days could be the suitable condition for cold tolerance evaluation of large-scale peanut germplasm by the comprehensive membership function analysis and the standard normal distribution test according to the seed vigor of peanut cultivars after treatments at 10℃, 8℃, 6℃, and 4℃ for seven days. At seedling stage, after treatment at 6℃ for seven days, plant height, leaf area, fresh weight of aerial parts, fresh weight of root, dry weight of aerial parts, dry weight of root, and cold tolerance grade were measured to evaluate the cold tolerance of various peanut cultivars. Correlation analysis revealed that the leaf area, fresh weight of aerial parts and cold tolerance grade had the most significant relationships with cold tolerance and could be used as the main evaluation indicators for the identification of cold tolerance at seedling stage in peanut. In the field, cold tolerance of various cultivars were evaluated by emergence rate, emergence ability, and yield component factors through the early sowing and sowing by stages. Finally, based on the multiple phenotypic analysis, the most cold-tolerant peanut (cultivar NH5) and the most cold-sensitive peanut (cultivar FH18) were identified at germination and seedling stages, suitable for planting in Northeast China. This study provided the reference for peanut planting in high-latitude and cold regions and the excellent germplasm of cold tolerance mechanism in peanut.